Inorganic colored pigment and process of preparing the same



Patented Jan. 28, 1936 INQRGANIC COLORED PIGIVIEN'I' AND PROCESS OFPREPARING THE SAlVIE Erich Korinth, Frankfort-on-the-Main-Hochst,

and Georg Moder, Munster-in-Taunus, Germany, assignors to I. G.Farbenindustrie Aktiengesellschai't, Frankfort-on-the-Main, Germany N 0Drawing. Application February 3, 1932, Serial 'No. 590,775. In GermanyFebruary 11, 1931 11 Claims. (01.134 18) Our present .invention relatesto inorganic colored pigments and a process of preparing the same, moreparticularly it relates to pigments which are obtainable by thermalcombination of zinc oxide with an oxide of the type MeO, wherein Merepresents a metal of the group consisting of Cd, Mg, Fe and Mn, bywhich combination mixed crystals or solid solutions are formed.

- 'It is ,known that by heating zinc oxide with cobalt compounds,particularly with cobaltous oxide, an excellent green colored pigment,Rinnmanns green, is obtained. According to the researches of I. A.Hedvall (Zeitschrift fiir anorganische und allgemeine Chemie 1915, vol.92, page 201) this pigmentrepresents a solid solution of hexagonal ZnOand regular C00, from which solution is derived an isodimorphous seriesof mixed crystals (crystalized solid solutions). It is also known thatin a similar manner other metal oxides may be combined with C00,provided that the chemical type and. the lattice construction of theoxides permit such combination. Thus, for instance, a rose-colored mixedcrystal of the type MgO.CoO-has been prepared (compare; Zeitschriftfiiranorganische Chemie 1914, Vol.86, page 296). From MnO or M0 on the oneside and C00 on the other side there are obtained mixed crystals, thecolor of which shifts from yellow-green over green-brown to red'(Zeitschrift fiir anorganische Chemie and allgemeine Chemie 1915, vol.92, page 381).

We have now found that new pigments of a new structure are obtainable ifin the molecular construction forming the basis of the pigment Rinmnannsgreen the zinc oxide is retained but the cobaltous oxide is replaced byanother suitable metal oxide of an equivalent or similar type and of asimilar lattice construction. For the formation of such new pigments ofnew structure there may be used, hypothetically, one of the oxides ofthe elements of the isomorphous series (Nernst, Theoretische Chemie, 7thed. 1913, page 174), namely Zn, Cd, Mg, Fe, Mn, Co, Ni, Be, Ru, 0s, Pd,Ir, Cu, Ca, Re, Ma. 1

We have found that the elements Cd, Mg, Fe, and Mn are particularlyuseful and suitable for the purpose of the present invention. Our newpigments obtainable by thermal combination of ZnO with an oxide of thesaid elements possess coloring properties which are at least as good asthose of the pigment Rinnmanns green; their shades, however, differconsiderably from that of Rinnmanns green. Thus, for instance, anexcellent bright red color is obtained by replacing in Rinnmanns greenC00 by MnO. The replace-.

ment of C00 by FeO yields a series of olivecolored pigments. If C00 isreplaced by CdO, green-yellow pigments are formed; combination of ZnOwith MgO results in the formation of white pigments.

The thermal combination of the oxides may particularly advantageously beperformed by using as starting materials instead of the oxidesthemselves, suitable metal compounds capable of forming thecorresponding oxides. The metal oxides are thus formed by thermaldissociation during the formation of the pigments. We have found thatthe sulfates of the metals disclosed above are particularly useful .dueto their high decomposing point.

The duration and the temperature of the process for the formation of thepigments may be reduced by adding in known manner fluxes ormineralizers, for instance, KCl, NazSOa etc. The reaction between thecomponents is generally carried out at temperatures between about 800 C.and about 1100" 0. Higher temperatures may be used but are unnecessaryif the substances are heated to the said temperatures for a sufficienttime.- It is essential that the coloring metal oxide used forcombination with zinc oxide at the end' of the operation must be presentin the degree of oxidation corresponding with the formula MeO. If,therefore, a metal oxide of a higher degree of oxidation is used asstarting material, the heating operation has to be carred out in agaseous atmosphere having a reducing action sufficient for producing andmaintaining the state of oxidation of MeO.

The following examples serve to illustrate the invention but they arenot intended to limit it thereto; the parts are by weight:

1. (a) 94 parts of ZnS04.'7H2O and 6 parts of MnSOiAI'hO are intimatelymixed and heated to about 1000 C. in order to expel S03. The product isthen reduced so that the manganese is in the state of oxidation of MnO,for instance, by heating in a current of gas consisting of about percentby volume of CO and 50 percent by volume of CO2. There is obtained abeautiful, orange brown pigment of good fastness properties.

('b) By using 98 parts of ZnSOrfiHzO and 2 parts of MnSO4.4HzO there isobtained a fiery orange pigment if the heating operation is carried outin a reducing atmosphere in which MnO is stable.

(0) 99.4 parts of ZHSO4.7H2O and 0.3 part of MIISO4.4H2O yield on beingtreated as indicated under (a) a yolk colored pigment.

- MnSO4.4I-IzO yield a pigment of alight yellow color.

'2. By proceedi as there "are obtained from ZnSO'i and FeSOi, ac-

cording to proportion of iron, after the reduction dark olive-green tolight yellow-green pigments.

1 We claim: V r

1. The process of producing pigmentswhich comprises causingppractically,pure 'zinc oxide to combine with a metal oxide of the type MeO whereinMe represents a'metal of the group conare formed.

"25The processor producing pigments which ,7 comprises combiningpractically pure zincoxide anda metalv oxide of the type MeO, whereinjMerepresents a metal of the group consisting of Cd,

Mg,Fe andMIn to form mixed crystals orisolid solutions by'thermalcombinationof the com- 'pone'ntsat temperatures between about 800 C.

and about 1100 C;

T 3. The process of prod'ucing colored pigments which comprisescombining practically pure zinc oxide andferrous oxide to formmixedcrystals or solid solutionslby heating together zinc sulfate:andferrous sulfate at about 1000 C, and heating'the resulting product ina gaseous atmos pherehaviniga reducing actionto f orm the'oxide IFeOiwhichcomprises combining practically pure zinc 1 oxide and 'manganousoxide to form mixed crystals or solid solutions by heating together zinc"sulfatea'n'd manganous sulfate at about '10Q0 C. andfheating resultingproduct in a gaseous atmospherehavinga reducing action to form the 7 his5. As new 2,028,980 (d)- 99.8 parts oiZnSOifIHzO and 0.2 part ofindicated in Example 1;

V a gaseous atmosphere having a reducing: action s p to forrntheoxideMeOg 4.. I'he process of producing colored pigments products,inorganic, pigments com-T" prising mixed crystals containing intheirlatticeco tru t on i a l l e'zi c i s d an a metaljoxide "of thetype MeO, wherein Merepre--- sents'ametal of thegroup consisting of Cd,Mg,

Fe and Mn, which"ipigments are obtainableby .thennalcombination orthe-said metal oxides. 1

6. As new products, inorganic pigments con sisting of mixed crystalscontainingin their'lattice 7 construction practically pure zinc oxideand a metal oxide of the type MeO, wherein Me represents a metal of thegroup consisting of Cd, Mg; FeandMn.

'7'. As new products; inorganiccolored pigments, I

consisting of mixedcrystalscontainingv in their" lattice constructionpractically pure zinc oxide and ferrous oxide being obtainable bythermal combination of the said'oxides, which pigments possessdark-olive to light yellow green shades.

8. As new products, inorganic colored pigments lattice construction"practically pure zinc oxide consisting of mixed'crystals containing intheir 7 and manganous oxide being obtainableby ther .mal combination ofthe said oxides, which pigments' possess brown to red to yellow shades.

' 1 9. As a new product, a chestnut-brown to bright V red pigmentconsisting of mixedcrystals contain- "ing in their lattice constructionpractically pure zinc oxide and manganousoxide. V v '10. The process ofproducing pigments which and a metal oxide of the t pe MeO, wherein Merepresents a metal of the group consisting oiCd,

comprises combining practicallypure oxide Mg, Fe and Mn to form mixedcrystals or solid solutionsfby heating the components at temperaturesbetween about 800,? C. andaboutllQO? C; in

11 The process of producing pigments which comprises causing apractically pure zinc com- 7 pound, capable of forming zinc oxide bythermal dissociation to act upon a compound of: a metal form the oxideMeO.

V {GEORG Q

